Hydroxyproline Concentration And Associated Factors Of Preserved Smile-Derived Corneal Stromal Lenticules

To evaluate changes of hydroxyproline concentration and its influencing factors of SMILE-derived corneal stromal lenticules with different preservation methods. 

The study was in accordance with the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of the Eye and ENT Hospital of Fudan University. Written informed consent was acquired from all patients. A total of 390 lenticules of 195 patients who underwent SMILE operation in the Eye and ENT Hospital of Fudan University (Shanghai, China) from July 2023 to November 2023 were recruited in this study. 

390 corneal stromal lenticules of 195 patients were derived in small incision lenticule extraction (SMILE) surgeries. 30 of the lenticules were divided into the fresh (control) group, and the rest were randomly and evenly divided and stored in anhydrous glycerol, silicone oil, Optisol and cryopreservation for 1 day, 1 week or 1 month. Hydroxyproline assay kit (ab222941, Abcam) was used to measure the hydroxyproline concentration of each preservation. Concentrations of MMP-2, TIMP-2, TNFα, TGFβ2 and ROS were also evaluated.

In anhydrous glycerol group, the concentration of hydroxyproline decreased significantly within 1w, while which of silicone oil group remained stable within 1w, and decreased significantly in 1m. The sequence of hydroxyproline concentration in Optisol group was 1m > 1d > 1w. Hydroxyproline concentration in cryopreservation group decreased within 1m. Hydroxyproline concentration was highest in Optisol group and lowest in anhydrous glycerol group under the same preservation time. Hydroxyproline concentration was negatively correlated with MMP-2 (r=-0.16, P=0.421) and TIMP-2 (r=-0.56, P=0.002*),while MMP-2 and TNFα (r=0.17, P=0.242), TIMP-2 and TGFβ2 (r=0.21, P=0.207), and TNFα and ROS (r=0.52, P=0.007*) were positively correlated. 

More collagen was retained in SMILE lenticules preserved in Optisol under the same preservation time. The mechanism of the changes of collagen in preserved SMILE-derived lenticules and oxidative stress requires further investigation.